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    <title>Document</title>
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    <script>
        const obj = {
            uname: 'xiaoheizi',
        }

        Object.defineProperty(obj, 'age', {
            value: '2.5',
            writable: true,     // 默认值为false  不可改值    
            enumerable: true,   // 默认值为false   不可改删除
            configurable: true, // 默认值为false 不和重新定义
        })

        obj.age = '3.5'

        console.log(Object.keys(obj))
        console.log(obj)
    </script>
</body>

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